title: Exercise endurance in chronic obstructive pulmonary disease patients at an altitude of 2640 meters breathing air and oxygen (FIO2 28% and 35%): a randomized crossover trial.
abstract: BACKGROUND
  At Bogota's altitude (2640 m), the lower barometric pressure (560 mmHg) causes severe hypoxemia in COPD patients, limiting their exercise capacity. The aim was to compare the effects of breathing oxygen on exercise tolerance.
  
  
  METHODS
  In a blind, crossover clinical study, 29 COPD patients (FEV1 42.9 ± 11.9%) breathed room air (RA) or oxygen (FIO2 28% and 35%) during three treadmill exercise tests at 70% of their maximal capacity in a randomized order. Endurance time (ET), inspiratory capacity (IC), arterial blood gases and lactate were compared.
  
  
  RESULTS
  At the end of the exercise breathing RA, the ET was 9.7 ± 4.2 min, the PaO2 46.5 ± 8.2 mmHg, the lactate increased and the IC decreased. The oxygen significantly increased the ET (p < 0.001), without differences between 28% (16.4 ± 6.8 min) and 35% (17.6 ± 7.0 min) (p = 0.22). Breathing oxygen, there was an increase in the PaO2 and SaO2, higher with FIO2 35%, and a decrease in the lactate level. At "isotime" (ET at RA), with oxygen, the SpO2, the oxygen pulse and the IC were higher and the heart rate lower than breathing RA (p < 0.05).
  
  
  CONCLUSIONS
  Oxygen administration for COPD patients in Bogotá significantly increased ET by decreased respiratory load, improved cardiovascular performance and oxygen transport. The higher increases of the PaO2 and SaO2 with 35% FIO2 did not represent a significant advantage in the ET. This finding has important logistic and economic implications for oxygen use in rehabilitation programs of COPD patients at the altitude of Bogotá and similar altitudes.
authors.affiliation: 1Pulmonary Function Laboratory, Fundacion Neumologica Colombiana , Bogotá , Colombia.
authors.forename: Dario
authors.initials: D
authors.lastname: Maldonado
authors.forename: Mauricio
authors.initials: M
authors.lastname: González-García
authors.forename: Margarita
authors.initials: M
authors.lastname: Barrero
authors.forename: Claudia
authors.initials: C
authors.lastname: Jaramillo
authors.forename: Alejandro
authors.initials: A
authors.lastname: Casas
mesh_terms: D000368:Aged; D000388:Air; D000531:Altitude; D003105:Colombia; D018592:Cross-Over Studies; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006339:Heart Rate; D006801:Humans; D007320:Inspiratory Capacity; D019344:Lactic Acid / Q000097:blood; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000008:administration & dosage* / Q000097:blood; D010313:Partial Pressure; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D016037:Single-Blind Method; D013997:Time Factors
chemical_list: D019344:Lactic Acid; D010100:Oxygen
keywords: altitude; chronic obstructive pulmonary disease; endurance; exercise tolerance; hypoxemia; oxygen therapy